On Mon, Feb 11, 2013 at 7:02 PM, Pranith Kumar K <pkara...@redhat.com>wrote:
> hi, > Problem: > > When there are multiple fds writing to same file with eager-lock enabled, > the fd which acquires the eager-lock waits for > post-op-delay secs before doing the unlock. Because of this all other fds > opened on the file face extra delay when > performing writes. Eager-locking, post-op-delay need to be disabled when > there are multiple fds opened on the file. > > Here is the profile info output for the case above: > Execute the following command on the mount point. > for n in `seq 1 50` ; do eval > "/home/pranithk/workspace/**gerrit-repo/append2log.py > ./ben.log 10000 0.001 &" ; done ; wait > > %-latency Avg-latency Min-Latency Max-Latency No. of calls > Fop > --------- ----------- ----------- ----------- ------------ > ---- > 0.00 0.00 us 0.00 us 0.00 us 50 > RELEASE > 0.00 0.00 us 0.00 us 0.00 us 60 > RELEASEDIR > 0.00 55.00 us 55.00 us 55.00 us 1 > GETXATTR > 0.00 31.50 us 27.00 us 36.00 us 2 > STATFS > 0.00 41.00 us 29.00 us 53.00 us 2 > ENTRYLK > 0.00 198.00 us 198.00 us 198.00 us 1 > CREATE > 0.00 124.00 us 108.00 us 140.00 us 2 > READDIR > 0.00 27.04 us 17.00 us 95.00 us 49 > OPEN > 0.00 74.89 us 13.00 us 206.00 us 47 > STAT > 0.01 87.02 us 11.00 us 391.00 us 50 > FLUSH > 0.01 102.43 us 20.00 us 268.00 us 60 > OPENDIR > 0.02 344.27 us 22.00 us 940.00 us 44 > WRITE > 0.02 228.80 us 52.00 us 345.00 us 82 > FXATTROP > 0.03 199.89 us 19.00 us 404.00 us 120 > READDIRP > 0.05 91.41 us 23.00 us 832.00 us 421 > LOOKUP > 99.86 632698.45 us 17.00 us 1999724.00 us 126 > FINODELK > > Observe that most of the delay is in FINODELK fop. > > Possible Solution: > With the patch: http://review.gluster.org/4468 we started > maintaining open-fd count in the inode. We need to implement xdata based > xattr retrieval in write-fop and get open-fd-count in write fop. Remember > the open-fd-count received from the write-fops and maintain it in > afr-fd-ctx. If the open-fd count is >1 post-op-delay is immediately > disabled for that write fop. All write-fops take into consideration this > count to determine whether to enable eager-lock, post-op-delay for that > write fop. > > Let me know if you foresee any issues with this approach. > > https://bugzilla.redhat.com/**show_bug.cgi?id=910217<https://bugzilla.redhat.com/show_bug.cgi?id=910217>is > tracking this issue. > Ideally you would want open-fd count to be retrieved in all fops, and only when an eager lock has been acquired. Any fop callback's xattr_rsp inspection should potentially wake up the sleeping post-op-delay in that inode (and disable further eager locking temporarily). Avati
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